In prior art patents, there are disclosed various methods and apparatus for applying locking patches of resilient resin to internally threaded articles such as nuts, having openings at both ends of the threaded portions. In the devices disclosed in these patents, generally a rotatable table is disposed for receiving fasteners about the periphery of the table and transporting them through a plurality of stations to effect application of the patch to the internal threads of the fastener elements.
In U.S. Pat Nos. 4,054,688 and 4,100,882, there is provided a means whereby a portion of the heat fusible resin particles is deposited on one area of the hot threaded surface of an element, and thereafter, resin particles are deposited on a further area of the threaded surface to produce two distinct patches at a desired location. In each of the aforementioned patents, the internally threaded element is retained on the rotatable support member in a selected position by means of a slot which receives a portion of the external head of a hex headed nut, by way of example. After a discrete patch is applied to the internal threads of the fastener, a turning moment is applied to the fastener element to move it such that a different external surface of the hexagonal element is received by the slot, after which a second discrete patch is applied to the fastener.
U.S. Pat. No. 3,858,262 discloses a method and apparatus for making a self-locking threaded element which avoids the difficulties of resin deposit on the end faces of the threaded element and is effective to deposit resin on the threaded surface in the selected area with a minimum of spatter on other portions of the threaded surface. In that method and apparatus as disclosed, a nut or other internally threaded member is heated, and while mounted with its axis in an up-anddown position, the threaded surface is sprayed with finely divided resin particles which were caught and built up on the heated surface to form a plastic body.
In U.S. Pat. No. 3,894,509, there is disclosed an apparatus and method for mass production of such internally threaded elements including an automatic means to move a succession of internally threaded elements through various stations in which the elements are loaded onto a conveying and treating member. A resilient resin locking patch is formed on the threaded surface of the elements by deposition of heat fusible resin powder and thereafter, the elements are unloaded.
U.S. Pat. Nos. 3,416,492 and 4,366,190 discloses methods and apparatus wherein a self-locking internally threaded element is manufactured having a locking body of resilient resin provided over 360 degrees of arc of the internal threaded surface.
While the above referred to apparatus and methods have proved to be successful in achieving the objects for which they were intended, it has become desirable to have an improved method and apparatus which provides for superior control of the resin deposit or patch application including the area of the deposit, reduction of splatter and improved flow and efficient application of the resin powder. While the present invention will be described particularly with respect to applying heat softenable resin particles to the initial threads of internally threaded articles, it is to be understood that the apparatus and process of the present invention can be utilized to apply a variety of materials, including thermoplastic resins and thermoplastic resin compounds.
lt is therefore a desirable object of the present invention to provide an improved method and apparatus for the manufacture of self-locking internally threaded elements wherein the self-locking feature is obtained through a plastic resin deposited onto the internal surface of the element.
A further desirable object of the present invention is to provide an improved method and apparatus for the manufacture of internally threaded elements wherein improved control of the application of the locking body of resin is obtained over a desired arcuate and vertical area of the internal threads of the element.
A still further object of the invention is to provide an improved spray guide applicator having improved application, control and definition of the resin application over a desired arcuate and vertical area of the internal threads of internally threaded elements.